Signal-detecting devices and signal-transmitting devices are well known and are nowadays used increasingly in combination with glazings. This is particularly the case for glazings used in sophisticated, high value products, such as glazings used in automotive vehicles. The devices are positioned on the glazing in the inside of the vehicle, to transmit or receive signals through the glazing.
A signal-detecting device may, for example, be used to detect events or conditions occurring outside an automotive vehicle. The signal may, for example, be used to assess or detect changes in weather conditions (e.g. temperature, pressure, sunlight, rain, fog, mist, snow, ice), noise levels, vibration levels, sound levels, motion, etc. Typical sensors used in automotive vehicles include rain sensors (to activate windscreen wipers in wet weather conditions) and light sensors (to turn on headlights when entering a tunnel).
Alternatively the device may simply be a camera, for providing an enhanced rear view from a vehicle, or another sensor that is useful for monitoring or security purposes. For example, it may be a detector for a signal used to gain access to the vehicle, e.g. for a remote device used for unlocking a vehicle. The possibilities are extensive.
A signal-transmitting device may, for example, be used to transmit a signal allowing a vehicle to be identified or tracked. It may provide an image or display (e.g. for information, advertising or entertainment). It may transmit a light beam. Again, there are very many possibilities.
In some cases both a signal-transmitting device and a signal-receiving device may be used. For example, a signal may be transmitted from a vehicle and bounced back from another vehicle to a signal receiver. By determining the distance between the vehicles it can be determined if the vehicles are a safe distance apart for a given speed. If not, an alarm may be actuated. A similar system may be used to aid in parking a vehicle.
The nature of the signal to be detected or transmitted can vary with the device. The signal may, for example, be visible light, ultra-violet light, infra-red light, another wavelength of electromagnetic radiation, sound, vibration, temperature, pressure, etc., or a change in any of the foregoing. For example, a detector may be used to detect ultra-violet light above a given threshold intensity. Once this intensity has been exceeded a piece of equipment may be triggered (e.g. an alarm, an indicator, a fan or an automatic sun-shade). The precise nature of the signal-detecting and/or signal-receiving device is not crucial, provided that the signal can be detected or transmitted so as to provide a useful function.
Signal transmitting and receiving devices require a minimum optical transmission at various wavelengths in order to function. This is generally not a problem when the device is mounted on either a clear single ply of glass or a laminated glazing comprising a clear interlayer laminated between two plies of clear glass. However, laminated glazings often comprise a tinted or coloured interlayer, in either a shadeband region or throughout the glazing, providing a region which is relatively opaque at certain wavelengths. These relatively opaque regions can interfere with or block completely the transmission of certain signals, reducing the optical transmission below the minimum levels for the devices to function. For this reason signal transmitting/receiving devices are generally used with clear (non-tinted) glazings, or glazings having a slight tint or colour.
Rather than being restricted to using clear glazing with signal transmitting and receiving devices, the present invention allows an alternative approach to be taken.